1.4.2- Dithiazolium salts, reduction

All known reactions of this category have been reported in CHEC-II(1996). Notable examples include the carbene addition to l,3,4-oxathiazol-2-ones to give 1,4,3-oxathiazines the hydrogenation of l,4,2-dioxazol-2-one over Raney nickel to give amides and C02 and the reductive dimerization of several 1,4,2-dithiazolium salts with Zn dust to give the tetrathiadiazafulvalenes 66 and 67 <1996CHEC-II(4)515>. 

C4H2N3OS3] / CONHj Reduction of the parent 1,2,3-dithiazolium salt with Zn/ ACN EPR/ 295 N(3) 0.878 81Mayl/ 84Mayl... 

When 4-unsubstituted pyridinium salts were used, simultaneous chlorination accompanies the dithiazolium rings formation to give chlorinated salts 114 and radicals 115 after reduction in high yields (2002CC2562,2003JA14394 Scheme 57). 

The dithiazolium chloride 45 could be reduced directly with triphenylantimony to the radical 33 (Equation 7). This latter step gave poor yields (<15%) regardless of the choice of solvent (acetonitrile or liquid sulfur dioxide), reductant (Ag, Zn, Ph3Sb), or starting salt (chloride or hexafluoroantimonate). Radical 33 was best liberated by reduction of the crude salt with triphenylantimony <2004JA8256>. Once isolated, however, radical 33 is relatively air stable in the solid state. 

The 1,3,2-dithiazolium radicals 35, 36, and 46 generated in situ by reduction of corresponding salts with Ph Sb and tetrabutylammonium chloride in liquid sulfur dioxide <2005CC2366>, silver powder in dichloromethane <2004PS979>, and BU4NCI and Na2S204 in SO, <2005CC2366>, respectively. 

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